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<FONT color="green">001</FONT>    package register;<a name="line.1"></a>
<FONT color="green">002</FONT>    <a name="line.2"></a>
<FONT color="green">003</FONT>    import mathtools.Complex;<a name="line.3"></a>
<FONT color="green">004</FONT>    import mathtools.Matrix;<a name="line.4"></a>
<FONT color="green">005</FONT>    import exceptions.MatrixSizeException;<a name="line.5"></a>
<FONT color="green">006</FONT>    <a name="line.6"></a>
<FONT color="green">007</FONT>    /**<a name="line.7"></a>
<FONT color="green">008</FONT>     * Class Register is a one-dimensional Matrix which will hold the amplitudes of the Quantum <a name="line.8"></a>
<FONT color="green">009</FONT>     * state. <a name="line.9"></a>
<FONT color="green">010</FONT>     * @author Richard Inskip, Matt Cole<a name="line.10"></a>
<FONT color="green">011</FONT>     *<a name="line.11"></a>
<FONT color="green">012</FONT>     */<a name="line.12"></a>
<FONT color="green">013</FONT>    <a name="line.13"></a>
<FONT color="green">014</FONT>    public class Register extends Matrix {<a name="line.14"></a>
<FONT color="green">015</FONT>    <a name="line.15"></a>
<FONT color="green">016</FONT>            /** Number of states in the register */<a name="line.16"></a>
<FONT color="green">017</FONT>            private int numStates;<a name="line.17"></a>
<FONT color="green">018</FONT>            /** Number of qubits in the register */<a name="line.18"></a>
<FONT color="green">019</FONT>            private int numQbits;<a name="line.19"></a>
<FONT color="green">020</FONT>    <a name="line.20"></a>
<FONT color="green">021</FONT>            /**<a name="line.21"></a>
<FONT color="green">022</FONT>             * Constructor to create the Quantum Register depending on the number of Quantum bits.<a name="line.22"></a>
<FONT color="green">023</FONT>             * @param numQubits The number of Quantum bits.<a name="line.23"></a>
<FONT color="green">024</FONT>             */<a name="line.24"></a>
<FONT color="green">025</FONT>            public Register(int numQubits){<a name="line.25"></a>
<FONT color="green">026</FONT>                    super(1, (int)Math.pow(2,numQubits), 0);<a name="line.26"></a>
<FONT color="green">027</FONT>                    numStates = (int)Math.pow(2,numQubits);<a name="line.27"></a>
<FONT color="green">028</FONT>                    this.numQbits = numQubits;<a name="line.28"></a>
<FONT color="green">029</FONT>                    setToGroundState();<a name="line.29"></a>
<FONT color="green">030</FONT>            }<a name="line.30"></a>
<FONT color="green">031</FONT>            <a name="line.31"></a>
<FONT color="green">032</FONT>            /**<a name="line.32"></a>
<FONT color="green">033</FONT>             * Puts the register into the ground state. Called when the register is created and also used<a name="line.33"></a>
<FONT color="green">034</FONT>             * when the reset button is clicked on the UI.<a name="line.34"></a>
<FONT color="green">035</FONT>             */<a name="line.35"></a>
<FONT color="green">036</FONT>            public void setToGroundState() {<a name="line.36"></a>
<FONT color="green">037</FONT>                    m[0][0] = new Complex(1,0);<a name="line.37"></a>
<FONT color="green">038</FONT>                    for     (int j = 1; j &lt; numStates; j++){<a name="line.38"></a>
<FONT color="green">039</FONT>                            m[0][j] = new Complex(0,0);<a name="line.39"></a>
<FONT color="green">040</FONT>                    }<a name="line.40"></a>
<FONT color="green">041</FONT>            }<a name="line.41"></a>
<FONT color="green">042</FONT>    <a name="line.42"></a>
<FONT color="green">043</FONT>            /**<a name="line.43"></a>
<FONT color="green">044</FONT>             *       * A Method to update the Register with a new version. This will allow the Register object<a name="line.44"></a>
<FONT color="green">045</FONT>             * to always update itself.<a name="line.45"></a>
<FONT color="green">046</FONT>             * @param r A new 1-dimensional Vector to update the elements in the Register.<a name="line.46"></a>
<FONT color="green">047</FONT>             * @throws MatrixSizeException <a name="line.47"></a>
<FONT color="green">048</FONT>             */<a name="line.48"></a>
<FONT color="green">049</FONT>            public void update(Matrix r){<a name="line.49"></a>
<FONT color="green">050</FONT>                    /* Make sure the updating vector is of the same dimensions as the<a name="line.50"></a>
<FONT color="green">051</FONT>                     * current register.<a name="line.51"></a>
<FONT color="green">052</FONT>                     */<a name="line.52"></a>
<FONT color="green">053</FONT>                    if(r.getHeight()!= height &amp;&amp; r.getWidth()!= width){<a name="line.53"></a>
<FONT color="green">054</FONT>                            throw new IllegalArgumentException("The updating Register must be of exact size as the current Register.\n" +<a name="line.54"></a>
<FONT color="green">055</FONT>                                            "New register size: " + r.getHeight() + "Old register size: " + height);<a name="line.55"></a>
<FONT color="green">056</FONT>                    }<a name="line.56"></a>
<FONT color="green">057</FONT>                    else{<a name="line.57"></a>
<FONT color="green">058</FONT>                            // Set the elements of the updating register into the register.<a name="line.58"></a>
<FONT color="green">059</FONT>                            for(int j = 0; j &lt; numStates; j++){<a name="line.59"></a>
<FONT color="green">060</FONT>                                    setElement(0,j,r.getElement(0, j));<a name="line.60"></a>
<FONT color="green">061</FONT>                            }<a name="line.61"></a>
<FONT color="green">062</FONT>                    }<a name="line.62"></a>
<FONT color="green">063</FONT>            }<a name="line.63"></a>
<FONT color="green">064</FONT>    <a name="line.64"></a>
<FONT color="green">065</FONT>            /**<a name="line.65"></a>
<FONT color="green">066</FONT>             * A Method to update the Register.<a name="line.66"></a>
<FONT color="green">067</FONT>             * @param r A new 1-dimensional Vector to update the elements in the Register.<a name="line.67"></a>
<FONT color="green">068</FONT>             */<a name="line.68"></a>
<FONT color="green">069</FONT>            public void update(Complex [] r){<a name="line.69"></a>
<FONT color="green">070</FONT>                    /* Make sure the updating vector is of the same dimensions as the<a name="line.70"></a>
<FONT color="green">071</FONT>                     * current register. If the dimensions are different, throw a <a name="line.71"></a>
<FONT color="green">072</FONT>                     * exception (TODO).  <a name="line.72"></a>
<FONT color="green">073</FONT>                     */<a name="line.73"></a>
<FONT color="green">074</FONT>                    if(r.length != height &amp;&amp; r.length != width){<a name="line.74"></a>
<FONT color="green">075</FONT>                            throw new IllegalArgumentException("The updating Register must be of exact size as the current Register.\n" +<a name="line.75"></a>
<FONT color="green">076</FONT>                                            "New register size: " + r.length + "Old register size: " + getHeight());<a name="line.76"></a>
<FONT color="green">077</FONT>                    }<a name="line.77"></a>
<FONT color="green">078</FONT>    <a name="line.78"></a>
<FONT color="green">079</FONT>                    // Set the elements of the updating register into the register.<a name="line.79"></a>
<FONT color="green">080</FONT>                    for(int j = 0; j &lt; numStates; j++){<a name="line.80"></a>
<FONT color="green">081</FONT>                            setElement(0, j, r[ j]);<a name="line.81"></a>
<FONT color="green">082</FONT>                    }<a name="line.82"></a>
<FONT color="green">083</FONT>            }<a name="line.83"></a>
<FONT color="green">084</FONT>    <a name="line.84"></a>
<FONT color="green">085</FONT>            /** <a name="line.85"></a>
<FONT color="green">086</FONT>             * A Method to normalise the amplitudes of the Register.<a name="line.86"></a>
<FONT color="green">087</FONT>             * @throws MatrixSizeException <a name="line.87"></a>
<FONT color="green">088</FONT>             */<a name="line.88"></a>
<FONT color="green">089</FONT>            public void normalise(){<a name="line.89"></a>
<FONT color="green">090</FONT>                    double sum = 0.0;<a name="line.90"></a>
<FONT color="green">091</FONT>                    for(int j = 0; j &lt; numStates; j++){<a name="line.91"></a>
<FONT color="green">092</FONT>                            sum += getElement(0,j).getMagnitudeSquared();<a name="line.92"></a>
<FONT color="green">093</FONT>    <a name="line.93"></a>
<FONT color="green">094</FONT>                    }<a name="line.94"></a>
<FONT color="green">095</FONT>                    double normalisation_constant = 1/Math.sqrt(sum);<a name="line.95"></a>
<FONT color="green">096</FONT>                    Matrix normalised_register = multiplyMatrix(normalisation_constant);<a name="line.96"></a>
<FONT color="green">097</FONT>                    update(normalised_register);<a name="line.97"></a>
<FONT color="green">098</FONT>            }<a name="line.98"></a>
<FONT color="green">099</FONT>            /**<a name="line.99"></a>
<FONT color="green">100</FONT>             * Return the number of qubits in the register. This is NOT the number of states (or amplitudes)<a name="line.100"></a>
<FONT color="green">101</FONT>             * @return numQubits Number of qubits represented by the register<a name="line.101"></a>
<FONT color="green">102</FONT>             */<a name="line.102"></a>
<FONT color="green">103</FONT>            public int getNumQbits() {<a name="line.103"></a>
<FONT color="green">104</FONT>                    return numQbits;<a name="line.104"></a>
<FONT color="green">105</FONT>            }<a name="line.105"></a>
<FONT color="green">106</FONT>    <a name="line.106"></a>
<FONT color="green">107</FONT>            /**<a name="line.107"></a>
<FONT color="green">108</FONT>             * Return the number of states in the register, or number of amplitudes<a name="line.108"></a>
<FONT color="green">109</FONT>             * @return numberStates Number of states in the register<a name="line.109"></a>
<FONT color="green">110</FONT>             */<a name="line.110"></a>
<FONT color="green">111</FONT>            public int getNumStates(){<a name="line.111"></a>
<FONT color="green">112</FONT>                    return numStates;<a name="line.112"></a>
<FONT color="green">113</FONT>            }<a name="line.113"></a>
<FONT color="green">114</FONT>            <a name="line.114"></a>
<FONT color="green">115</FONT>            /**<a name="line.115"></a>
<FONT color="green">116</FONT>             * Return the probability of a given state. Needed for drawing graph of probabilities<a name="line.116"></a>
<FONT color="green">117</FONT>             * @param state State to give probability for<a name="line.117"></a>
<FONT color="green">118</FONT>             * @return probability Probability of measuring given state<a name="line.118"></a>
<FONT color="green">119</FONT>             */<a name="line.119"></a>
<FONT color="green">120</FONT>            public double getProbabilityOfState(int state){<a name="line.120"></a>
<FONT color="green">121</FONT>                    return m[0][state].getMagnitudeSquared();<a name="line.121"></a>
<FONT color="green">122</FONT>            }<a name="line.122"></a>
<FONT color="green">123</FONT>            <a name="line.123"></a>
<FONT color="green">124</FONT>            <a name="line.124"></a>
<FONT color="green">125</FONT>            /**<a name="line.125"></a>
<FONT color="green">126</FONT>             * Post measurement. Returns the state that has probability 1.<a name="line.126"></a>
<FONT color="green">127</FONT>             * @return i State that has probability 1 or hence measure state<a name="line.127"></a>
<FONT color="green">128</FONT>             */<a name="line.128"></a>
<FONT color="green">129</FONT>            public int postMeasure() {<a name="line.129"></a>
<FONT color="green">130</FONT>                    for(int i = 0; i &lt; numStates; i++) {<a name="line.130"></a>
<FONT color="green">131</FONT>                            if (this.getProbabilityOfState(i)==1 ){<a name="line.131"></a>
<FONT color="green">132</FONT>                                    return i;<a name="line.132"></a>
<FONT color="green">133</FONT>                            }<a name="line.133"></a>
<FONT color="green">134</FONT>                    }<a name="line.134"></a>
<FONT color="green">135</FONT>                    throw new RuntimeException("Register has not been measured correctly. No certain state.");<a name="line.135"></a>
<FONT color="green">136</FONT>            }<a name="line.136"></a>
<FONT color="green">137</FONT>    }<a name="line.137"></a>
<FONT color="green">138</FONT>    <a name="line.138"></a>
<FONT color="green">139</FONT>    <a name="line.139"></a>




























































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